1. Field of the Invention
The invention relates to an apparatus and method for automatically processing logs so that the logs are processed to obtain a yield that approaches optimum for a particular cutting pattern and log shape.
2. Prior Art
Prior art automatic log processing apparatus are known, typical apparatus being shown in U.S. Pat. Nos. 3,452,246; 3,554,249 and 3,736,968, the respective inventors being Ottosson, Arnels and Mason. These patents disclose automatic apparatus for processing logs, and for some shapes of logs, optimum yield is not obtained due to the scanning and cutting limitations of the apparatus. To obtain approximate profile and length data of a log, prior art apparatus usually scan the log dimensionally in one reference place only, commonly a horizontal plane. Then, based on this data, spacing between the saws, chippers, etc. can be adjusted automatically by a control means, which is commonly a digital computer programmed to determine saw spacing for optimum yield from the data. However, such data is limited to the reference plane in which the log is scanned, and highly irregular logs, such as badly crooked logs or logs with tapers which vary considerably in different planes, cannot be cut optimally by such apparatus. One difficulty is that in such apparatus there is no provision for shifting the log in a controlled manner in a plane normal to the reference plane, eg. shifting the log vertically.
U.S. Pat. No. 4,147,259, inventor Uno B. Nilsson, discloses a feed mechanism for logs in which the logs are gripped by scissor clamps mounted on two carriages running on overhead rails. After scanning, the log is initially positioned accurately by a log charging device, and the scissor clamps are automatically "floated" to accomodate the position of the log prior to enagagement. Upon engagement by the clamps, it is assumed that there is negligible shifting of the log out of the desired orientation, so that the clamps are considered to maintain the log in the desired orientation achieved by the charging device.